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Installation
A proper sequencing installation requires two or more Gardner Denver rotary air compressors complete
with AUTO SENTRY W controllers, piped into a common air system, interconnected as described above.
For best performance, the units must be piped directly to the receiver, without any intervening check
valves, dryers, or other restrictions. The receiver should also be sized to prevent excessive drops or
rapid rises in pressures during the operation as described below. All standard practices common to
sound air compressor installations such as proper sizing of discharge piping, proper electrical supply and
conductor sizing, and grounding are to be observed. The serial communications interface meets RS-485
standards, the most widely used interface in harsh, industrial environments today. However it is still
recommended that the communications cables be routed through metallic conduit to provide them with
both mechanical protection and electromagnetic shielding.
Each expansion circuit board has two modular jacks which accept RJ-12 telephone plugs. One jack is
vacant, the other has a short pigtail plugged into it. To interconnect two compressors, plug the cable into
the vacant jack on each controller. For installations of more than two units, the pigtail plug must be
disconnected on all controllers except the two at each end of the communications line. The order of
interconnection has no effect on the system operation. The following conditions are necessary and
sufficient for proper operation:
1.
Every compressor must have a cable connecting it to another compressor. One less cable than the
number of units sequenced must be used.
2.
Each board that has only one cable connected to it must have its pigtail plugged into the unused
jack. All installations will have two such units.
Operation
1.
ESTABLISHING THE INITIAL SEQUENCE
Operation of compressors in sequence requires only selection of the sequence operating mode during
adjustments and a press of the [RUN] key on each compressor in the system. Since the sequencing
algorithm includes provisions for automatic replacement of a failed master or ’lead’ compressor, it is
important for the operator to be aware of the hierarchy of events when starting the system.
The first compressor placed into sequence mode will become the master. However, since any
compressor first placed into sequence has no way of knowing whether or not a master exists, it will first
assume the highest rotation number available. For example if the number of units to be sequenced is
programmed at four, any compressor will start out in position four when placed in sequence mode. It will
then listen on the communications line for a call from the master.
If no call is received, it will assume position three and again wait for a call from the master. After another
lack of a master call, it assumes position two. Subsequently, it assumes position one which makes it the
master. As soon as a master is established, it immediately attempts to call all other units and assigns
them successive rotation positions. The system is now active.
Before a master is established, the system is not deprived of air. This is due to one of the outstanding
features of the AUTO SENTRY W sequencing system: pressure control is always executed locally at
each individual compressor. The effective unload point for compressor control is the programmed unload
point minus 3 (rotation number - 1). So while compressors count down towards establishing a master,
they are also capable of delivering air at a pressure determined by the above formula.
To ensure that two or more machines do not simultaneously decrement their rotation numbers and
simultaneously become masters, it is advisable to place the desired master in sequence mode first and
wait until the first decrement in rotation number is seen (about 7 seconds) before placing subsequent
compressors in sequence mode. If it is desired to dictate the complete initial sequence manually, wait
until the previous machine decrements one position and then place the next desired compressor in
Содержание PUREAIR EWC99C
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